33 Seismic Imaging of the San Andreas Fault in Northern California using Receiver Functions

Scattering of teleseismic body waves is conventionally used to investigate crustal and mantle structure using the so-called “receiver function” technique. This approach makes use of the fact that teleseismic events have nearvertical incidence upon horizontally layered structure, ensuring minimum phase, and assumes that source-time functions can be approximated by energy on the P component of motion. This approach has been successful in countless applications, including the characterization of layered crust and mantle, anisotropy and dipping structure. Results from a recent application of the receiver function method near Parkfield in Northern California suggest that crustal structure is highly anisotropic with some indication of shallow offset in crustal discontinuities across the San Andreas Fault (SAF) (Ozacar and Zandt, 2009). Here we use receiver functions to analyze crustal structure around the SAF near San Juan Bautista in Northern California by decomposing radial and transverse signals into first order harmonic modes. Variations of energy of the different modes with depth are then used to characterize teleseismic wave scattering from velocity contrasts across the San Andreas Fault.